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  • 1
    Electronic Resource
    Electronic Resource
    The Twofold Heck Reaction on 1,2-Dihalocycloalkenes and Subsequent 6π-Electrocyclization of the Resulting (E, Z, E)-1,3,5-Hexatrienes: A New Formal {2+2+2}-Assembly of Six-Membered Rings (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1521-1534 
    Details
    ISSN: 1434-193X
    Keywords: Heck reaction ; Cross coupling ; Palladium ; Catalysis ; 6π-Electrocyclization ; Cyclohexa-1,3-dienes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,6-Disubstituted (E, Z, E)-1,3,5-hexatrienes (4 and 5) were prepared by vicinal twofold Heck coupling reactions from 1,2-dibromocyclopentene (1), 1,2-dibromocyclohexene (2), 1,2-diiodocyclopentene (8), 1,2-diiodocyclohexene (9), 1-bromo-2-trifluoromethanesulfonyloxycyclohex-1-ene (11), or 1-chloro-2-nonafluorobutanesulfonyloxycyclohex-1-ene (19) with alkenes 3, e. g. methyl, tert-butyl, menthyl, 8-phenylmenthyl acrylate, styrene, and alkenylsilanes, respectively, in moderate to mostly good and very good yields (20-92 %). The coupling of alkenylsilanes 3f-k could only be achieved with the 1,2-diiodocycloalkenes 8 and 9, respectively. The corresponding hexatrienes 5 with two different substituents in the 1- and 6-positions were prepared by a sequence of two coupling reactions with different alkenes from 1-chloro-2-nonafluorobutanesulfonyloxycyclo-hex-1-ene (19) or by Wittig-Horner-Emmons olefination of 2-bromocyclohexene-1-carbaldehyde (24) and subsequent Heck reaction of the resulting (E,Z)-bromodienes 25. Several of the hexatrienes (4aa, ee, 5aa, ee, al, am, el) readily underwent a 6π-electrocyclization upon heating in an inert atmosphere to give the 5- or 6-ring-annelated cis-5,6-disubstituted cyclohexadienes 26, 27 (50-95 %). Starting from 5am 2,3-disubstituted tetrahydronaphthalene 28am was formed under oxidative conditions (air) in the reaction and in the work-up procedure. The bissilyl-substituted derivatives 4ff, jj, 5ff did not cyclize under thermal conditions, apparently due to the steric demand of the two silyl substituents which would have to end up cis with respect to each other in the cyclohexadiene products.
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  • 2
    Electronic Resource
    Electronic Resource
    Palladium-Catalyzed Self-Cross Coupling of o-Bromo-trans-stilbenes To Yield 9,10-Bis(arylmethylene)-9,10-dihydroanthracenes© (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2289-2299 
    Details
    ISSN: 1434-193X
    Keywords: Palladium ; Cross coupling ; Arenes ; Cyclizations ; Polycycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under Palladium catalysis [Pd(OAc)2, K2CO3, LiCl, Bu4NBr, DMF] o-bromo-trans-stilbene (trans-7a) reacts to give 9,10-dibenzylidene-9,10-dihydroanthracene (4a) with formation of a new six-membered ring. The (Z) diastereomer crystallizes preferentially to give pure (Z)-4a, as proved by X-ray crystal structure analysis. A variety of substituted o-bromostilbenes and heterocyclic analogs 7 were prepared by Wittig olefination of o-bromobenzaldehyde with substituted benzyltriphenylphosphonium ylides, Wittig-Horner-Emmons olefination of arenecarbaldehydes with diethyl o-bromobenzylphosphonate or Wittig olefination of substituted benzaldehydes with substituted (o-bromobenzyl)-diphenylphosphonium ylides, respectively. The cis-o-bromostilbenes were photoisomerized to the trans diastereoisomers trans-7 by irradiation in the presence of diphenyl disulfide. All of these o-bromo-trans-stilbenes trans-7a-g and trans-7j, k under palladium catalysis reacted to the corresponding 9,10-bis(arylmethylene)-9,10-dihydroanthracenes 4, mostly as mixtures of (E) and (Z) diastereomers (50-97 % yield). The (Z) diastereomer of the parent 4a and the alkyl-substituted compounds 4c and 4e could be purified by simple crystallization, and in some runs, only (Z)-4a, c, e were obtained. Among the heterocyclic analogs trans-7h, i only the furyl derivative trans-7h reacted (76 % yield) cleanly, whereas the pyridine analog trans-7i gave a mixture of products from which the rather sensitive product 4i could not be isolated in pure form. The cis-o-bromostilbenes cis-7a, c cyclized to phenanthrenes under the same conditions (70-71 % yield). The UV spectra of compounds 4a, c-k are similar to that of anthracene, and so are the oxidation and reduction potentials of (Z)-4a.
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  • 3
    Electronic Resource
    Electronic Resource
    Convenient Preparation of α-Amino Acids with Bicyclopropylidene and Other Methylenecyclopropane Moieties (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2785-2795 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Bicyclopropylidene ; Methylenespiropentane ; Spiro compounds ; Organolithium derivatives ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic bicyclopropylidenyl- (rac-11) and methylenespiropentyl- (rac-17) substituted alanines have been synthesized by iodination of bicyclopropylidenyl- and methylenespiropentylmethanols 7, 13, nucleophilic substitution of the iodine in 8, 14 with the enolate of ethyl α-(diphenylmethyleneamino)acetate (O'Donnell's glycine equivalent) and deprotection of 9, 15 in 24 and 18% overall yield, respectively. N-Methylbicyclopropylidenylalanine rac-22, was obtained from the Michael adduct of (bicyclopropylidenyl)magnesium bromide 18 to enamine 19 and deprotection of the carbamate 20 (23% overall yield). Racemic (1-amino-2-methylenespiropentane)- (37), (1-amino-2-methylenecyclopropane)- (3), and (1-aminobicyclopropylidene)carboxylic acid (39) were prepared as hydrochlorides by tert-butoxycarbonylation of the lithiated methylenespiropentane (6), methylenecyclopropane (4), or bicyclopropylidene (5) intermediates with di-tert-butyl pyrocarbonate (Boc2O), repeated lithiation of the tert-butyl esters 29, 30, and 33 with LDA and subsequent carboxylation, Curtius degradation of the half esters 31, 32, and 34 followed by deprotection in 11, 45, and 4% overall yields, respectively. Compound 37 was also prepared from bicyclopropylidene (5) following the same procedure, but with rearrangement in the last but one step, in 19% overall yield. An attempted Hofmann degradation of the bicyclopropylidenecarboxamido ester 40 with NBS failed and gave only bromohydrin 44 (27%), but with bis(acetoxy)iodobenzene provided carbamate 46a, b in 76 amd 79% yield, respectively. Along this route with subsequent deprotection of 46b, the amino acid 39 could be prepared in up to 10% overall yield from bicyclopropylidene.
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  • 4
    Electronic Resource
    Electronic Resource
    Nickel- and Palladium-Catalyzed Cross-Coupling Reactions at the Bridgehead of Bicyclo[1.1.1]pentane Derivatives - A Convenient Access to Liquid Crystalline Compounds Containing Bicyclo[1.1.1]pentane Moieties (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1137-1155 
    Details
    ISSN: 1434-193X
    Keywords: Bicyclo[1.1.1]pentane ; Haloarenes, cross-coupling of ; Propellanes ; Palladium ; Catalysis ; Small-ring systems ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Radical addition reactions of organyl iodides 7a-s onto [1.1.1]propellane (2) followed by halogen-lithium exchange and transmetallation with zinc chloride, as well as additions of Grignard reagents to 2, have furnished a variety of 3-substituted bicyclo[1.1.1]pentyl-1-magnesium (14) and -zinc (19) derivatives. The latter have been coupled with various alkenyl, aryl, and biaryl halides and triflates under NiCl2dppe, Pd(PPh3)4, or PdCl2(dppf) catalysis to give a number of 1,3-disubstituted bicyclo[1.1.1]pentyl derivatives 17, 20, and 23, several of which exhibit liquid crystalline properties, in moderate to very good yields. The coupling products 20ca, 23ab, 23ae, 23ff, and 23fg have been further transformed to yield bicyclo[1.1.1]pentyl derivatives 32, 24ab, 24ae, 27ff, and 27fg, respectively, bearing alkynyl, cyano, and/or alkenyl groups.
    Additional Material: 7 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Convenient Syntheses of Novel α- and β-Amino Acids with Spiropentyl Groups (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3105-3115 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Spiro compounds ; Michael addition ; Copper reagents ; Curtius degradation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic spiropentylglycine (8) has been synthesized by sodium borohydride reduction of benzyl (E/Z)-2-chloro-2-spiropentylideneacetate (5-Bn), nucleophilic substitution of the chlorine in the product 6 with azide and hydrogenolytic deprotection of the resulting 7 (overall yield 15%). An alternative approach to 8 consisted of the coupling of the higher-order cuprate 10, generated by halogen-metal exchange from bromospiropentane (9), with the electrophilic glycine equivalent 11 followed by deprotection (overall yield 47%). Enantiomerically pure (1′-aminospiropentyl)acetic acid [(R)-16] (overall yield 16% from 5-Me) and 1-aminospiropentanecarboxylic acid [(R)-23] (29% from 5-Me) were obtained from the Michael adduct 14-Me of (4R,5S)-4,5-diphenyloxazolidin-2-one (13) and methyl (E/Z)-2-chloro-2-spiropentylideneacetate (5-Me). Racemic 1-aminospiropentanecarboxylic acid (R/S-23) was prepared by rhodium-catalyzed addition of dimethyl diazomalonate to methylenecyclopropane and subsequent Curtius degradation of the halfester 28 via the azide 29 (overall yield 14%). Upon standing in aqueous solution, 23 underwent complete rearrangement to the new 1-amino-2-methylenecyclobutanecarboxylic acid (24). The interesting derivative of azabicyclo[3.1.0]hexane-1-carboxylate 34 with an annelated spiropentane moiety and a β-amino acid fragment was incidentally obtained in a one-step intermolecular domino reaction starting with the addition of lithium benzylamide to methyl 2-chloro-2-cyclopropylideneacetate (32, 41% yield).
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  • 6
    Electronic Resource
    Electronic Resource
    An Easy Access to 1-Azaspiropentane-2-carboxamides - The First Derivatives of a New Type of Amino Acids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2017-2024 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Azaspiropentanes ; Heterocycles ; Peptides ; Strained molecules ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azaspiropentanecarboxamides 10 and 12 are formed with remarkable ease in two steps in a one-pot operation from methyl 2-chloro-2-cyclopropylideneacetate (4) by addition of a primary amine in tetrahydrofuran and subsequent treatment with sodium hydride/triethylamine in the presence of another equivalent of a primary amine or ammonia. Achievable yields of the amides 10, 12 were moderate to good (27-59%, 12-48%), while the corresponding esters 9 could only be obtained in poor yields (4-14%). The new α-amino acid amides are surprisingly stable, and they can be incorporated into small peptides as demonstrated with the preparation of the glycine 13e and the spirocyclopro-paneoxazoline derivative 14e.
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  • 7
    Electronic Resource
    Electronic Resource
    Ring Opening of Methylenecyclopropane Moieties in the Palladium-Catalyzed Cross-Coupling of Methylenecyclopropyl Bromides with Metallated CH-Acidic Compounds (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 453-457 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Bicyclopropylidene ; Methylenecyclopropane ; Palladium catalysis ; Zinc reagents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Palladium-catalyzed cross-coupling reactions of bromo(methylenecyclopropanes) 1c, 2c with the sodium enolate of dimethyl malonate 4a and the chlorozinc enolates of the glycine equivalent (diphenylmethyleneamino)acetate 4c and diethyl malonate 4d, respectively, have been found to proceed with opening of the three-membered ring in each case, to give the corresponding dienyl-substituted CH-acidic compounds 5-7 in moderate to good yields. On the other hand, coupling of bicyclopropylidenylzinc chloride (2d) with diethyl bromomalonate (4e) and the electrophilic glycine equivalent ethyl 2-acetoxy-2-(diphenylmethyleneamino)acetate (4f) gave 7 and 6 in 27 and 29% yield, respectively.
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  • 8
    Electronic Resource
    Electronic Resource
    Surprisingly Facile Addition of Thiols to the Double Bonds of Bicyclopropylidene and Other Methylenecyclopropanes (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1535-1542 
    Details
    ISSN: 1434-193X
    Keywords: Radical reactions ; Spiro compounds ; Additions ; Sulfides ; Amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of thiols 8a-h onto the double bonds of bicyclopropylidene (1) and methylenespiropentane (2) proceeds quantitatively in benzene at 20 to 75 °C in the absence of catalysts or radical initiators to give products 9, 10 with complete retention of both three-membered rings. Methylenespiropentane (2) yields exclusively the anti-Markovnikov adduct 10. The unsubstituted methylene-cyclopropane (3) gives 9% of the ring-opened compound 12 in addition to the anti-Markovnikov adduct 11. The addition of thiols to n-heptylbicyclopropylidene (13), methylenecyclopropylacetic acid (15), and the amino acids 17, 19 containing bicyclopropylidene or methylenespiropentane fragments, does not proceed stereoselectively, though in all cases the mercapto function adds to the double bond with retention of the cyclopropane ring to give interesting new amino acids containing bicyclopropyl and spiropentyl fragments, respectively. The probable mechanism of this thiol addition is discussed in the light of a test with the cyclizing intramolecular addition of 2-(2-methylenecyclopropyl)ethanethiol 27.
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  • 9
    Electronic Resource
    Electronic Resource
    Palladium-Catalyzed Bicyclization of 2-Bromo-1,6-dienes and -1,6-enynes to 5-Membered-Ring-Annelated Vinylcyclopropane Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1333-1344 
    Details
    ISSN: 1434-193X
    Keywords: Cross-coupling ; Isomerizations ; Cycloisomerization ; Palladium ; Homogeneous catalysis ; Bicyclic vinylcyclopropanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Palladium-catalyzed cyclizations of the 2-bromo-1,6-diene 6 with an acetoxymethyl substituent on the bromoalkenyl moiety did not only lead to the expected 1-acetoxymethyl-1,3-diene 40 but also to the bicyclic vinylcyclopropane 35, the 1,3-diene 36 and the triene 37 (a dendralene). All these compounds result from an initial 5-exo-trig cyclization of the 2-bromo-1,6-diene. By proper choice of the reaction conditions (ligand, base, allylic leaving group) each of these compounds could be formed selectively. Small amounts (3-5%) of the isomerized 1-acetoxymethyl-1,3-diene 38 and the 6-endo product 39 were also isolated. With the acetoxymethyl substituent on the alkenyl moiety (compound 27) only the 1,4-diene 44 was formed. The related 1,6-enyne 57 with a methoxycarbonyloxymethylene substituent on the triple bond gave in 36% yield the 2,3-bis(bicyclo[3.1.0]hex-1-yl)-substituted 1,3-butadiene 63, which can be regarded as a dehydrodimer of the vinylcyclopropane 35. The presumption that the formation of 63 involves the alkenylpalladium species 65 was supported by its successful inter- as well as intramolecular trapping with formate as a hydride source to yield the vinylcyclopropane 35. The reaction pathways leading to the vinylcyclopropane derivatives 35 and 63 have in common that an alkylpalladium species rather undergoes a 3-exo-trig cyclization than an internal rotation followed by a β-hydride elimination.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98406_s.pdf or from the author.
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  • 10
    Electronic Resource
    Electronic Resource
    Cyclopropyl Building Blocks for Organic Synthesis, 42.Part 41: B. Anichini, A. Goti, A. Brandi, S. I. Kozhushkov, A. de Meijere, Synlett 1997, 25-26. - Part 40: V. Chaplinski, H. Winsel, M. Kordes, A. de Meijere, Synlett 1997, 111-114. An Unprecedented Mode of Ring Opening of Methylenecyclopropane Moieties - Reactions of Methylenecyclopropanecopper Reagents with an Electrophilic Glycine Equivalent (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2197-2204 
    Details
    ISSN: 0947-3440
    Keywords: Bicyclopropylidene ; Spiro compounds ; Cycloadditions ; Amino acids ; Cuprates ; Tetrahydropyridines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of ethyl 2-acetoxy-2-diphenylmethyleneaminoacetate (1) with organocopper reagents derived from bicyclopropylidene (2) and methylenecyclopropane (3) are accompanied by an unusual mode of opening of one three-membered ring to give 4-methylene-1,2,3,4-tetrahydropyridine derivatives 8a, 9 in good yields. The cuprate derived from methylenespiropentane (4) reacts with 1 to yield both the normal substitution product 14 (37%) as well as the rearrangement product 15 (34%), while the simple cyclopropylcuprate undergoes substitution to give the protected cyclopropylglycine 16 (75%) without rearrangement. The tetrahydropyridine 8a shows an interesting tautomerism in solution. The 4-cyclopropylidenetetrahydropyridine 15 undergoes an unusual dehydrodimerization to produce two separable rotamers, C2-19 and C1-19, via 18.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971105
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